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Zn Ions (zn + ion)

Distribution by Scientific Domains
Chemistry66%
Physics and Astronomy13%
Earth and Environmental Science13%

Selected Abstracts

Structure of aminopeptidase N from Escherichia coli complexed with the transition-state analogue aminophosphinic inhibitor PL250

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2009
Marie-Claude Fournié-Zaluski
Aminopeptidase N (APN; EC 3.4.11.2) purified from Escherichia coli has been crystallized with the optically pure aminophosphinic inhibitor PL250, H3N+ -CH(CH3)-P(O)(OH)-CH2 -CH(CH2Ph)-CONH-CH(CH2Ph)CO2,, which mimics the transition state of the hydrolysis reaction. PL250 inhibits APN with a Ki of 1.5,2.2,nM and its three-dimensional structure in complex with E. coli APN showed its interaction with the S1, S,1 and S,2 subsites of the catalytic site. In this structure, the Zn ion was shown to be pentacoordinated by His297, His301 and Glu320 of APN and the two O atoms of the phosphinic moiety of PL250. One of these O atoms is also involved in a hydrogen bond to Tyr381, supporting the proposed role of this amino acid in the stabilization of the transition state of the enzymatic process. The strength of the phosphinic zinc binding and the occupancy of the S,2 subsite account for the 100-fold increase in affinity of PL250 compared with the dipeptide-derived inhibitor bestatin (Ki = 4.1 × 10,6,M). Accordingly, the removal of the C-terminal phenylalanine of PL250 resulted in a large decrease in affinity (Ki = 2.17 × 10,7,M). Furthermore, it was observed that the C-terminal carboxyl group of the inhibitor makes no direct interactions with the amino acids of the APN active site. Interestingly, PL250 exhibits the same inhibitory potency for E. coli APN and for mammalian enzymes, suggesting that the structure of the complex could be used as a template for the rational design of various human APN inhibitors needed to study the role of this aminopeptidase in various pathologies. [source]

Optical investigations on the existence of phase transition in ZnO:Li thin films prepared by DC sputtering method

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 3 2008
A. Abu EL-Fadl
Abstract We investigated the effect of temperature on the absorption spectra of Zn0.8Li0.2O thin films (ZnO:Li), deposited at 573 K, in the wavelength range 190-800 nm. The films were deposited on sapphire, MgO or quartz substrates by DC sputtering method. The results show a shift of the optical energy gap (Eg), with direct allowed transition type near the fundamental edge, to lower wavelengths as the temperature increases. The temperature rate of Eg changes considerably showing an anomaly around 320 K depending on type of substrate. The founded results indicated that replacement of Zn ions with Li ions induces a ferroelectric phase in the ZnO wurtzite-type semiconductor. The exponential dependence of the absorption coefficient on the incident photon energy suggests the validity of the Urbach rule. (© 2007 WILEY -VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

A Study of the Influence of Composition on the Microstructural Properties of ZnO/Al2O3 Mixed Oxides,

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2009
Shaojun Miao
Abstract A series of ZnO/Al2O3 mixed oxide samples with varyingZn/Al ratio is prepared by coprecipitation, ageing, drying, and calcination. Samples are investigated in the state after drying and calcination. The applied methods include X-ray diffraction, solid-state 27Al magic-angle spinning nuclear magnetic resonance spectroscopy, transmission electron microscopy and thermogravimetric experiments coupled with evolved gas analysis. Phases present in the dried precursor samples include hydrozincite, zaccagnaite, and an unknown phase. After calcination zinc oxide and spinel can be found. All results indicate the substitution of Al ions for Zn ions in zinc oxide of zinc-rich samples. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

Di-2-pyridyl Ketone Oxime in Zinc Chemistry: Inverse 12-Metallacrown-4 Complexes and Cationic Pentanuclear Clusters

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 10 2005
Maria Alexiou
Abstract The use of di-2-pyridyl ketone oxime (Hpko)/X, "blends" (X, = PhCO2,, N3,, NCO,, acac,, NCS,) in zinc chemistry yields neutral tetranuclear and cationic pentanuclear clusters. Various synthetic procedures have led to the synthesis of compounds [Zn4(OH)2(O2CPh)2(pko)4]·3MeCN (1·3MeCN), [Zn4(OH)2(N3)2(pko)4]·4DMF (2·4DMF), [Zn4(OH)2(NCO)2(pko)4]·3DMF·H2O (3·3DMF·H2O), [Zn4(OH)2(acac)2(pko)4]·4CH2Cl2 (4·4CH2Cl2), [Zn5Cl2(pko)6][ZnCl(NCS)3]·2.5H2O·1.5MeOH (5·2.5H2O·1.5MeOH) and [Zn5(NCS)2(pko)6(MeOH)][Zn(NCS)4]·2.5H2O·MeOH (6·2.5H2O·MeOH). The structures of the six complexes have been determined by single-crystal X-ray crystallography. The tetranuclear molecules of 1,4 lie on a crystallographic inversion centre and have an inverse 12-metallacrown-4 topology. Two triply bridging hydroxides are accommodated in the centre of the metallacrown ring. The pko, ligands form a propeller configuration that imposes absolute stereoisomerism with , and , chirality. Two metal ions are in distorted O2N4 octahedral environments, whereas the rest are in severely distorted tetrahedral or trigonal bipyramidal environments. The five Zn ions of the cations of 5 and 6 are held together by six pko, ligands which adopt three different coordination modes; the chloro (5) and isothiocyanato (6) ligands are terminal. The five Zn ions define two nearly equilateral triangles sharing a common apex, and the novel Zn5 topology can be described as two "collapsed" 9-metallacrown-3 structures sharing a common Zn apex. Besides the pentanuclear cations, the structures of 5 and 6 contain slightly distorted tetrahedral [ZnCl(NCS)3]2, and [Zn(NCS)4]2, ions, respectively, with the isothiocyanato ligands binding the metal ion in a virtually linear fashion. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

Zinc ion adsorption on montmorillonite,Al hydroxide polymer systems

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 2 2003
R. P. T. Janssen
Summary Clay,Al hydroxide polymers (CAlHO) can bind heavy metals effectively and may play an important role in the adsorption behaviour and metal binding capacity of soils. We studied the dependence of Al loading and pH on the adsorption of Zn on Na-saturated montmorillonite,Al hydroxide polymer systems. The available binding sites on Al hydroxide polymers (AlHO) had a very strong affinity for Zn ions. Zinc binding on the clay surface became important when the binding sites on the AlHO were nearly all occupied. The pH had a very strong effect on the Zn binding. At pH 6.6 much more Zn could be adsorbed to the AlHO than at pH 5.0. The effect of the Al:clay ratio on Zn binding was influenced by pH. At pH 6.6, Zn binding to the AlHO, expressed per mole AlHO, was independent of the Al:clay ratio, whereas at pH 5.0 this relation was dependent. This is related to the constant charge of the AlHO at pH 6.6, whereas at pH 5.0 the charge decreases with increasing Al:clay ratio. If clay,Al hydroxide polymers are present in the soil their Zn binding to the AlHO will strongly influence the availability of the Zn. [source]

Effects of chromium stress on the subcellular distribution and chemical form of Ca, Mg, Fe, and Zn in two rice genotypes

JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 1 2010
Fanrong Zeng
Abstract A hydroponic experiment was carried out to study effects of chromium (Cr) stress on the subcellular distribution and chemical form of Ca, Mg, Fe, and Zn in two rice genotypes differing in Cr accumulation. The results showed that Ca, Mg, Fe, and Zn ions were mainly located in cell walls and vacuoles in roots. However, large amounts of metal ions were transferred from the vacuole to the nucleus and to other functional organelles in shoots. Chromium concentrations in the nutrient solution of 50 ,M and above significantly decreased Ca concentrations in the chloroplast/trophoplast, the nucleus, and in mitochondria. It further increased Mg concentrations in the nucleus and in mitochondria, as well as Zn and Fe concentrations in the chloroplast/trophoplast. These Cr-induced changes in ion concentrations were associated with a significant reduction in plant biomass. It is suggested that Cr stress interferes with the functions of mineral nutrients in rice plants, thus causing a serious inhibition of plant growth. The chemical forms of the four nutrients were determined by successive extraction. Except for Ca, which was mainly chelated with insoluble phosphate and oxalic acid, Mg, Zn, and Fe were extractable by 80% ethanol, d-H2O, and 1,M NaCl. The results indicated that these low,molecular weight compounds, such as organic acids and amino acids, may play an important role in deposition and translocation of Mg, Zn, and Fe in the xylem system of rice plants. [source]

Functional analysis of the heavy metal binding domains of the Zn/Cd-transporting ATPase, HMA2, in Arabidopsis thaliana

NEW PHYTOLOGIST, Issue 1 2009
Chong Kum Edwin Wong
Summary ,,The Zn/Cd-transporting ATPase, HMA2, has N- and C-terminal domains that can bind Zn ions with high affinity. Mutant derivatives were generated to determine the significance of these domains to HMA2 function in planta. ,,Mutant derivatives, with and without a C-terminal GFP tag, were expressed from the HMA2 promoter in transgenic hma2,hma4, Zn-deficient, plants to test for functionality. ,,A deletion mutant lacking the C-terminal 244 amino acids rescued most of the hma2,hma4 Zn-deficiency phenotypes with the exception of embryo or seed development. Root-to-shoot Cd translocation was fully rescued. The GFP-tagged derivative was partially mis-localized in the root pericycle cells in which it was expressed. Deletion derivatives lacking the C-terminal 121 and 21 amino acids rescued all phenotypes and localized normally. N-terminal domain mutants localized normally but failed to complement the hma2,hma4 phenotypes. ,,These observations suggest that the N-terminal domain of HMA2 is essential for function in planta while the C-terminal domain, although not essential for function, may contain a signal important for the subcellular localization of the protein. [source]

Mössbauer studies of Fe-Zn sulphur spinels

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 12 2007
Sung Hwan Bae
Abstract The polycrystalline sample of Zn doped Fe1,xZnxCr2S4(x = 0.1, 0.3) were prepared by solid state reaction. The crystal structure was determined to be the normal cubic spinel of space group Fd 3m and the lattice constants(x = 0.1, 0.3) were a0 = 9.9967(3) Å and a0 = 9.9926(3) Å, respectively. The magnetic moment values of Fe1,xZnxCr2S4 for the x = 0.3 were observed higher than that of the x = 0.1. The Néel temperatures were decreased to 153 K (x = 0.1), 135 K (x = 0.3) with Zn substitution concentration. This result is due to the decrease of A-B superexchange interaction by the replacement of Zn ions for A site. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Structure of Ga2O3(ZnO)6: a member of the homologous series Ga2O3(ZnO)m

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 5 2008
Yuichi Michiue
The structure of Ga2O3(ZnO)6 was determined using single-crystal X-ray diffraction techniques in the space group Cmcm. The metal ion sublattice resembles some of the Zn ions in the wurtzite ZnO structure. The oxygen ion sublattice in Ga2O3(ZnO)6 also resembles some of the O ions in ZnO. Structural relationships between Ga2O3(ZnO)6 and ZnO are discussed, illustrating the process for obtaining the centrosymmetric Ga2O3(ZnO)6 structure from the noncentrosymmetric ZnO. Structures of phases in the homologous series Ga2O3(ZnO)m are predicted on the basis of the structural data for Ga2O3(ZnO)6. The structures of even m are constructed by simply extending the structure units seen in Ga2O3(ZnO)6, while those of odd m consist of structure units which are of different types from those used for even m. [source]

A novel O,Zn bridging polymer complex of 2,6-bis[bis(carboxylatomethyl)aminomethyl]-4-methylphenolate

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2008
Yuan-Yuan Zhang
A new one-dimensional coordination polymer, catena -poly[[acetatohexaaqua{,4 -2,6-bis[bis(carboxylatomethyl)aminomethyl]-4-methylphenolato}trizinc(II)] octahydrate], [Zn3(C17H17N2O9)(C2H3O2)(H2O)6]·8H2O, is a trinuclear complex consisting of three zinc centers joined by a phenolate bridge and Zn(H2O)4 units. In each complex polymer unit, the three Zn atoms have different coordination modes. Of the two phenolate-bridged Zn ions, one adopts a distorted octahedral coordination composed of two carboxylate ligands, one tertiary N atom, two water molecules and the bridging phenolate ligand, while the other adopts a pyramidal geometry composed of two carboxylate ligands, one tertiary N atom from another coordination arm, one acetate anion as the counter-anion and the bridging phenolate ligand. The third type of Zn centre is represented by two independent Zn atoms lying on inversion centres. They both have an octahedral coordination consisting of four O atoms from four water molecules and two acetate carbonyl O atoms from the ligand. The latter Zn atoms join the above-mentioned binuclear complex units through O atoms of the carboxylate groups into an infinite chain. Neighboring aromatic rings are distributed above and below the chain in an alternating manner. Between the coordination chains, the Zn...Zn separations are 5.750,(4) and 6.806,(4),Å. The whole structure is stabilized by hydrogen bonds formed mainly by solvent water molecules. [source]

Structure of the Taz2 domain of p300: insights into ligand binding

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 12 2009
Maria Miller
CBP and its paralog p300 are histone acetyl transferases that regulate gene expression by interacting with multiple transcription factors via specialized domains. The structure of a segment of human p300 protein (residues 1723,1836) corresponding to the extended zinc-binding Taz2 domain has been investigated. The crystal structure was solved by the SAD approach utilizing the anomalous diffraction signal of the bound Zn ions. The structure comprises an atypical helical bundle stabilized by three Zn ions and closely resembles the solution structures determined previously for shorter peptides. Residues 1813,1834 from the current construct form a helical extension of the C-terminal helix and make extensive crystal-contact interactions with the peptide-binding site of Taz2, providing additional insights into the mechanism of the recognition of diverse transactivation domains (TADs) by Taz2. On the basis of these results and molecular modeling, a hypothetical model of the binding of phosphorylated p53 TAD1 to Taz2 has been proposed. [source]

A neutron crystallographic analysis of T6 porcine insulin at 2.1,Å resolution

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 10 2009
Wakari Iwai
Neutron diffraction data for T6 porcine insulin were collected to 2.1,Å resolution from a single crystal partly deuterated by exchange of mother liquor. A maximum-likelihood structure refinement was undertaken using the neutron data and the structure was refined to a residual of 0.179. The hydrogen-bonding network of the central core of the hexamer was observed and the charge balance between positively charged Zn ions and their surrounding structure was interpreted by considering the protonation and/or deprotonation states and interactions of HisB10, water and GluB13. The observed double conformation of GluB13 was essential to interpreting the charge balance and could be compared with the structure of a dried crystal of T6 human insulin at 100,K. Differences in the dynamic behaviour of the water molecules coordinating the upper and lower Zn ions were observed and interpreted. The hydrogen bonds in the insulin molecules, as well as those involving HisB10 and GluB13, are discussed. The hydrogen/deuterium (H/D) exchange ratios of the amide H atoms of T6 porcine insulin in crystals were obtained and showed that regions highly protected from H/D exchange are concentrated in the centre of a helical region of the B chains. From the viewpoint of soaking time versus H/D-exchange ratios, the amide H atoms can be classified into three categories. [source]

Crystallization and preliminary X-ray diffraction studies of an alcohol dehydrogenase from the Antarctic psychrophile Moraxella sp.

ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 2 2005
TAE12
An NAD+ -dependent psychrophilic alcohol dehydrogenase (ADH) from the Antarctic psychrophile Moraxella sp. TAE123 has been purified to homogeneity. The enzyme consists of four identical subunits, each containing two Zn ions. Protein crystals suitable for X-ray diffraction were obtained under optimized salting-out crystallization conditions using ammonium sulfate as a precipitating agent. The crystals are hexagonal bipyramids and belong to space group P3121 or P3221, with unit-cell parameters a = 136.4, c = 210.7,Å. They contain one protein homotetramer in the asymmetric unit. Diffraction data were collected to 2.2,Å under cryogenic conditions using synchrotron radiation. [source]